Edexcel International A Level Physics
Edexcel International A Level Physics Nuclear Decay Exam Questions
Free Edexcel International A Level Physics exam questions for Nuclear Decay, with a mark scheme for every pack. Covers background radiation, alpha, beta and gamma decay, nuclear equations, random decay, activity, decay constant, half-life, binding energy, fission and fusion.
Nuclear Decay exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel International A Level Physics Nuclear Decay
Nuclear decay is part of Unit 5: Thermodynamics, Radiation, Oscillations and Cosmology in Edexcel International A Level Physics. It covers the properties of alpha, beta and gamma radiation, background radiation, nuclear equations and the random, spontaneous nature of decay. You model decay mathematically with A = λN, N = N0 e^(-λt) and half-life, and use mass deficit and binding energy per nucleon to explain energy release in fission and fusion. It builds on Nuclear and particle physics in Unit 4. Examiners commonly ask for half-life calculations, correcting for background count and explaining why fusion needs extreme conditions.
What you need to know
- Types of radiation Alpha particles are helium nuclei, highly ionising and stopped by paper; beta particles are fast electrons or positrons stopped by a few mm of aluminium; gamma rays are electromagnetic, weakly ionising and very penetrating.
- Background radiation Always measure and subtract background count rate. Sources include radon, rocks, cosmic rays and medical procedures.
- Decay equations Activity A = λN; N = N0 e^(-λt); t½ = ln 2/λ. Decay is random and spontaneous.
- Nuclear equations Nucleon number and proton number are conserved; beta decay includes a neutrino or antineutrino.
- Binding energy Mass deficit is the difference between the mass of separated nucleons and the nucleus; binding energy = c^2Δm.
- Fission and fusion Fission of heavy nuclei and fusion of light nuclei increase binding energy per nucleon, releasing energy. Fusion requires very high temperature and density to overcome electrostatic repulsion.
Common mistakes in Nuclear Decay
- Not subtracting background count rate from measurements.
- Using a half-life in hours with an activity in becquerels without converting to seconds.
- Writing t½ = λ ln 2 instead of ln 2/λ.
- Saying decay rate can be changed by heating the source. Decay is spontaneous and unaffected by external conditions.
- Describing binding energy as the energy stored in a nucleus rather than the energy needed to separate it into nucleons.
Try three Nuclear Decay exam-style questions
1. A source has an initial activity of 800 Bq and a half-life of 6.0 hours. Calculate its activity after 15 hours. (3 marks)
Show the mark scheme answer
λ = 0.693/6.0 = 0.116 h^-1; A = 800 e^(-0.116 × 15); A = 1.4 × 10^2 Bq (141 Bq).
2. Explain what is meant by radioactive decay being random and spontaneous. (2 marks)
Show the mark scheme answer
Random: it is impossible to predict which nucleus will decay next or when, only a probability; spontaneous: decay is not affected by external factors such as temperature or pressure.
3. Explain why nuclear fusion requires very high temperatures. (3 marks)
Show the mark scheme answer
Nuclei are positively charged and repel each other; they must get close enough for the strong nuclear force to act; very high temperature gives nuclei enough kinetic energy to overcome the electrostatic repulsion.
Nuclear Decay FAQs
What does Edexcel International A Level Physics Nuclear decay cover?
It covers alpha, beta and gamma radiation, background radiation, nuclear equations, exponential decay and half-life, binding energy, fission and fusion.
Which unit is Nuclear decay examined in?
It is examined in Unit 5: Thermodynamics, Radiation, Oscillations and Cosmology.
What equations do I need for Nuclear decay?
Learn A = λN, N = N0 e^(-λt), t½ = ln 2/λ and ΔE = c^2Δm, and practise using ln graphs to find λ from count rate data.
